A one-cell reuse cellular system that performs communication using the same frequency in all cells has been adopted as a standard in recent years since the system enhances frequency use efficiency and improves the maximum transmission speed in each cell. However, there is a problem that, because the same frequency is used in adjacent cells, due to the influence of interference coming from an adjacent cell, particularly the communication quality of a terminal apparatus positioned at a cell edge is deteriorated.
Interference Alignment (IA) has been proposed as an effective method of reducing interference in such a one-cell reuse cellular system (for example, see NPL 1). IA is technology that calculates a transmit weight and a receive weight by each of a plurality of transmitters (for example, base station apparatuses) and each of a plurality of receivers (for example, terminal apparatuses) in a cooperative manner such that the directions (vectors) of equivalent channels of interference signals coming from the transmitters serving as interference sources become orthogonal to the receive weight to be multiplied by receive signals in the receivers, and that performs transmission/reception using these transmit/receive weights. By performing such control, even in the case where interference signals, the number of which is greater than or equal to a number removable by the receivers (the degree of freedom) comes from adjacent cells, it becomes possible to remove these interference signals and to highly accurately extract desired signals from the receive signals.
Here, the case in which control is performed to enable a terminal apparatus in each cell to remove interference signals coming from a plurality of base station apparatuses has been described by way of example. In contrast, it is also possible to enable a base station apparatus in each cell to remove interference signals coming from a plurality of terminal apparatuses individually positioned in a plurality of cells.
In addition, such technology can be used to reduce interference between cells with different zone radii in a system in which there is a plurality of picocells or femtocells in a macrocell.